The present invention relates to connectors for printed-circuit cards, and more particularly, to an improved connector which is intended to electrically connect the conductors on printed-circuit cards or boards to conductors on a printed-circuit type connection panel.
Obviously, such connectors need to reduce, to a minimum, the length of the conductors which are utilized with the circuits. If the length of the conductors are too long, the conductors will introduce, into the circuit, electrical characteristics which are likely to cause a substantial alteration in the electrical characteristics of the circuits which they interconnect, and which may possibly introduce inductive coupling or undesirable capacitance between the circuits.
Techniques used at the present time to produce compact circuits make it possible to reduce considerably the size of the majority of the electrical circuits contained in data-processing or other equipment. Such compact circuits are often produced in the form of printed circuits. Multiple layers of these printed circuits are sometimes combined into removable cards and into connection panels which are designed to hold connectors and to provide electrical connection between the circuits on different cards. To provide the electrical connections between the circuits on the cards and the circuits in the connection panels, it is essential to use connectors. Such connectors group together a very large number of contact members in a very small space.
Numerous connectors are known in which the contact members, which provide the electrical connections, are formed by flexible, conductive blades or pins that are relatively long and are often folded back on themselves. These contact members are adapted to provide adequate pressure against the contact surfaces by their own elasticity. When such connectors electrically connect together circuits through which pass electrical pulses containing components of very high frequency, the parts of the connectors through which these pulses flow often have the disadvantage that they introduce breaks in the impedance-matching and the looped or folded form of certain portions of the contact members often gives rise to undesirable inductive coupling between the circuits.
The connector arrangement described in U.S. Pat. No. 3,609,463 has as an object to overcome these disadvantages of these known conectors. As disclosed in that patent, electrical connection is provided by means of connectors in which the conductive portions are of remarkably small length and in which the conductive surfaces providing the contact are each subject, at a number of points, to mechanical pressure which is exerted by means of mechanical members independent of the electrical circuits. In the case envisaged, where the conductors utilized with printed circuits on the removable cards and with the connection panel, may be compared to sections of transmission line of a predetermined characteristic impedance, another object of U.S. Pat. No. 3,609,463 is to provide a connector, described above, in which the length of a conductive member capable of presenting a different characteristic impedance locally is fairly small so that the resulting disadvantages will be negligable or non-existent.
In accordance with the objects of U.S. Pat. No. 3,609,463, there is described in that patent an arrangement to connect circuits on printed-circuit cards to circuits on a printed-circuit connection panel wherein the panel supports a plurality of connectors arranged parallel to and at a distance from one another so as to allow a card to be inserted between two consecutive connectors and to be held in position perpendicularly to the panel. Each connector described in the patent is characterised in that it includes, at least on a side which corresponds to that face of the printed circuit card provided with contact areas, a row of flexible, conductive contact blades. One part of each of the contact blades is soldered to a conductive area on the connection panel and another part located against a contact area on the printed circuit card. A row of push members is arranged so that each is able to slide in a seating disposed opposite a contact blade. A row of springs is arranged so that each biases a push member against a contact blade and in turn biases the contact blade against a corresponding contact area on the printed circuit card. In an advantageous embodiment described in U.S. Pat. No. 3,609,463, contact blades are formed by metal strips carried by a thin sheet of insulating material that is common to all the contact blades associated with one connector.
An arrangement consisting of such connectors allows an assembly of compact circuits to be produced in which contact is provided between circuits with the maximum safety while at the same time, causing a minimum disturbance to the electrical characteristics of the circuits.
However, the presence of push members in this patented arrangement is attended by a certain disadvantage. Firstly, the push member increases the size of each connector, thus setting a limit to the density of the integrated circuit cards which can be connected together. Furthermore, because of the space which the push members take up, they restrict the possible number of contact areas. Moreover, because of their relative rigidity, the push members expose the metal contact strips, whose supporting sheet they place under tension, to considerable wear as a result of the rubbing which accompanies the insertion and withdrawal of the printed circuit cards. Finally, the insulating push members give rise to undesirable capacitance between the springs and the metal contact strips.
The improved connector of the present invention overcomes these disadvantages. As in the invention described in U.S. Pat. No. 3,609,463, the present invention relates an arrangement for connecting circuits on printed circuit cards to circuits on a printed circuit connection panel wherein the panel supports a plurality of connectors arranged parallel to and at a distance from one another so as to allow a card to be inserted between two consecutive connectors and to be held in position perpendicularly to the panel. Each improved connector includes at least on a side corresponding to that face of a printed circuit, a card which is provided with contact areas, a row of flexible, conductive contact blades which are formed by conductive strips carried on one face of a thin, common insulating sheet and a row of springs. One part of each of the contact blades is soldered to a conductive area on the connection panel and another part of the contact blades is located against a contact area on the printed circuit card. Each of the springs is intended to press one of the contact blades against a corresponding contact area on the printed circuit card and is characterised in that it presses directly against the opposite face of the common insulating sheet that which carries the conductive strips.
Thus, in the improved connector of the present invention, the push members are dispensed with and as a result, the connectors may be made smaller in size and the density of the printed circuit cards and the contact areas increased. Furthermore, the springs may be made less stiff than the push members and this permits the springs to yield easily under the pressure of the printed circuit cards which cuts down the wear on the contact blades.
In an advantageous embodiment of the present invention, each spring has two bosses to apply pressure to the corresponding contact blade at two separate points. Moreover, the connection panel may include a grounded lug connected to the various springs, and in this way, undesirable capacitance is suppressed.
The FIGURES in the accompanying drawings will provide good understanding of how the invention may be put into effect.